09-08-2013, 03:28 PM
Studies on Cercospora canescens Ell. and Mart causing leaf spot disease of greengram (Vigna radiata)
ABSTRACT
Cercospora canescens was inoculated onto different aged (20-70 days old) plants of green gram (cv. Shalimar Mung-1). The later was found invariably susceptible at all its growth stages with incubation period of 6-7 days and leaf spot diameter of 7.1-7.4 mm as recorded after 15 days of inoculation. Total sugar content showed an increasing trend and ranged from 124 to 129 and 133 to 135 mg/g dry weight during pre- and post-flowering periods respectively. The total phenol content also increases with plant age and was maximum (26.5 mg/g dry weigh) in 60 days old plants following which an insignificant decrease (26.5 mg/g dry weight) was recorded. Twenty five genotypes of greengram were screened for resistance against the pathogen under field conditions. The genotypes showed an indifferent response to invasion by C. canescens and none showed absolute resistance. However, five genotypes viz., ML-935, PDM-54, Pusa Vishal, SM-710 and SM-366 were moderately susceptible and manifested lower disease intensity (27.5-30.4 %) and disease incidence (34-35.4 %).